The subject matter described herein relates generally to wind turbines and, more particularly, to a method and apparatus for increasing lift on a wind turbine blade.
Wind turbines convert the kinetic energy of wind into electrical energy. Wind turbines include one or more blades that rotate when oncoming wind strikes the blades. The flow of wind over the wind turbine blades generates lift and provides torque to generate power. As such, the amount of energy that a wind turbine can extract from the wind is directly related to the lift generated on the blades. The amount of lift generated on the blades depends on a number of factors. These factors include a speed of the wind, a lift coefficient of the blades, a planform area of the blades, and an air density of the wind.
One technique that is used to increase lift, and thereby increase energy extracted by the wind turbine, is to increase the planform area of the blades. However, larger blades are more expensive, and may present structural issues in the wind turbine due to their greater weight. An additional technique for increasing lift is to pitch the blades such that an angle of attack is increased, thus increasing the lift coefficient. However, increasing the angle of attack above a critical angle of attack may result in air flow separation over the blades, thus stalling the blades. When stall occurs, lift generated by the blades decreases significantly and a large component of the torque is lost.